It will require a zombie dummy head and arms, which you can sew together if you want, and some wooden beams to make it appear that they are keeping the zombie from breaking through the window. Add some dark paint to the boards to make them look older in the low light of night, and place some bloody handprints on the beams. Attach the beams to the window in the formation of a tic-tac-toe board with the zombie in the center.
If you have a issues with space, then this tree made from scaffolding wood is the perfect fix for you. ~ If anyone knows the original link for this idea please post it in the comment section, Thank You